The invention relates generally to antifreeze, deicing, or freeze control compositions comprising at least one alkaline earth metal or alkali metal salt, for example, sodium nitrate, magnesium nitrate, or calcium nitrate.
Antifreeze and deicing agents are widely used to remove ice from or prevent the formation of ice upon surfaces such as roadways and equipment. The most widely used antifreeze and deicing agents contain sodium chloride or magnesium chloride. Due to the chlorine content, such chlorine containing antifreeze and deicing agents can cause significant damage to concrete, masonry, and metal surfaces, such as ferrous metal, when brought into aqueous solutions. Chlorine containing antifreeze and deicing agents are also detrimental to plants because chlorine is known to hinder the water uptake by roots of trees and lower plants.
Freeze control agents are widely used to prevent aggregates, such as coal, from freezing during transport in railcars, trucks, or barges. The freeze control agents are sprayed on the aggregates prior to or during loading of products into transport vessels. The most commonly used freeze control agents for this application contain calcium chloride. Again, due to the presence of chlorine, such calcium chloride containing freeze control agents have been shown to damage transport equipment and to increase the rate of corrosion in coal fired burners and power plants.
Ethylene glycol was formerly employed as a freeze control agent. Dowell M185 was sold commercially by Dowell division of Dow Chemical for many years for this purpose. Dowell M185 is a 60% ethylene glycol solution. Due to environmental concerns with ethylene glycol, this material is no longer sold for use as antifreeze for coal.
In an attempt to circumvent the corrosion issues associated with chlorine containing substances, diethylene glycol (DEG) has been employed as a freeze control agent. However, DEG is more expensive than calcium chloride and therefore, is not a cost-effective treatment for preventing freezing of aggregates. For example, the cost of treatment of one ton of coal with DEG can be two or three times greater than treatment with calcium chloride. Also, DEG is understood to be less effective as antifreeze for coal than ethylene glycol.
Therefore, there exists a long felt need for a freeze control composition that is economical to prepare and does not cause or accelerate corrosion. Additionally, there also exists a long felt need for antifreeze and deicing agents that do not cause or accelerate corrosion and are not detrimental to plants.
As defined in this disclosure, the term “antifreeze” is defined herein as an antifreeze, deicing, or freeze control composition. As defined in this disclosure, the term “aggregates” is defined herein as a plurality of any substance transported in bulk, such as coal, gravel, and grain.